When a person gets in a vehicle or a device, in order to prevent a passenger from separating from the vehicle or the device by collision between vehicles or with another object, various safety apparatuses are provided.
One typical safety apparatus among the various apparatuses is a seat belt, and the seat belt stably fixes the abdominal region and the breast of a passenger that gets in the vehicle or the device to a seat. However, as a result of a large collision between vehicles or with another object, even if a passenger wears a seat belt, the passenger is often wounded.
Therefore, various technology has been developed for a seat belt to exhibit its predetermined function even if a large collision between vehicles or with another object occurs. One such technology among various technology that has recently come to the fore is a pretensioner for improving a function and effect of a seat belt by introducing a webbing to the seat belt when a collision occurs between vehicles or when a vehicle collides with another object.
The pretensioner generally moves a rack adjacent to a micro gas generator (MGG) with a driving force generated in the MGG and rotates a pinion connected to a spool and thus introduces the webbing wound in the spool.
In this case, in order for the rack to rotate a pinion while moving, the rack and the pinion engage and thus at a first time point of starting transfer of a driving force from the MGG, a strong force is transferred to the pinion and thus the pinion may be deformed or broken. When the pinion is deformed or broken, a problem that the pretensioner cannot stably transfer a driving force to the spool occurs.
Further, the MGG generally uses explosive power obtained by exploding gunpowder therein as a driving force, but because gas generated while gunpowder explodes is not completely discharged, when operating a load limiter, a problem that an overshoot load occurs in operation loads of a webbing may occur.
That is, after the pretensioner operates, even if a webbing is locked by an emergency locking retractor (ELR) operating part, an operation load of the webbing is applied to a passenger by an inertial force, and the operation load of the webbing continuously increases and thus the passenger may be wounded. The load limiter appropriately withdraws a webbing to prevent the injury, but when gas is not completely discharged from the pretensioner, as described above, movement of the rack is disturbed and thus a rotation of the pinion connected to the spool is also disturbed, whereby withdrawing of the webbing is disturbed. Due to disturbance of withdrawing of the webbing, an overshoot load occurs in operation loads of the webbing generated when operating the load limiter, which is the above-described problem.